.\" Copyright (c) 2011 Kai Wang
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.\" $Id: dwarf_add_frame_fde.3 3640 2018-10-14 14:09:13Z jkoshy $
.\"
.Dd September 26, 2011
.Dt DWARF_ADD_FRAME_FDE 3
.Os
.Sh NAME
.Nm dwarf_add_frame_fde
.Nd add a call frame descriptor to a DWARF producer instance
.Sh LIBRARY
.Lb libdwarf
.Sh SYNOPSIS
.In libdwarf.h
.Ft "Dwarf_Unsigned"
.Fo dwarf_add_frame_fde
.Fa "Dwarf_P_Debug dbg"
.Fa "Dwarf_P_Fde fde"
.Fa "Dwarf_P_Die die"
.Fa "Dwarf_Unsigned cie"
.Fa "Dwarf_Addr virt_addr"
.Fa "Dwarf_Unsigned code_len"
.Fa "Dwarf_Unsigned symbol_index"
.Fa "Dwarf_Error *err"
.Fc
.Ft "Dwarf_Unsigned"
.Fo dwarf_add_frame_fde_b
.Fa "Dwarf_P_Debug dbg"
.Fa "Dwarf_P_Fde fde"
.Fa "Dwarf_P_Die die"
.Fa "Dwarf_Unsigned cie"
.Fa "Dwarf_Addr virt_addr"
.Fa "Dwarf_Unsigned code_len"
.Fa "Dwarf_Unsigned symbol_index"
.Fa "Dwarf_Unsigned end_symbol_index"
.Fa "Dwarf_Addr offset_from_end_sym"
.Fa "Dwarf_Error *err"
.Fc
.Sh DESCRIPTION
Function
.Fn dwarf_add_frame_fde_b
adds the call frame descriptor referenced by argument
.Ar fde
to a producer instance.
.Pp
Argument
.Ar dbg
should reference a DWARF producer instance allocated using
.Xr dwarf_producer_init 3
or
.Xr dwarf_producer_init_b 3 .
.Pp
Argument
.Ar fde
should reference a frame descriptor allocated using
.Xr dwarf_new_fde 3 .
.Pp
Argument
.Ar die
is ignored by this implementation of the
.Lb libdwarf .
.Pp
Argument
.Ar cie
specifies the index of call frame common information entry for
the frame descriptor.
Valid indices are those returned by the function
.Xr dwarf_add_frame_cie 3 .
.Pp
Argument
.Ar symbol_index
specifies the ELF symbol index of the first symbol to be used for
relocation.
.Pp
The meaning of the arguments
.Ar virt_addr ,
.Ar code_len
and
.Ar offset_from_end_sym
depend on the value of argument
.Ar end_symbol_index :
.Bl -bullet
.It
If the argument
.Ar end_symbol_index
is zero, the argument
.Ar virt_addr
specifies the relocatable address of the start of the function
associated with the frame descriptor, the argument
.Ar code_len
specifies the size in bytes of the machine instructions for this
function, the argument
.Ar symbol_index
specifies the ELF symbol to be used for relocating the address in
argument
.Ar virt_addr ,
and the argument
.Ar offset_from_end_symbol
is ignored.
.It
If the argument
.Ar end_symbol_index
is non-zero, it specifies the ELF symbol index of the second symbol to
be used for relocation.
In this case, the argument
.Ar virt_addr
specifies an offset from the relocatable symbol specified by argument
.Ar symbol_index ,
the argument
.Ar offset_from_end_symbol
should specify an offset from the symbol named by the argument
.Ar end_symbol_index ,
and the argument
.Ar code_len
will be ignored.
The
.Dv DW_DLC_SYMBOLIC_RELOCATIONS
flag should also have been set on the DWARF producer instance.
.Pp
Application code can retrieve the relocation entries for the symbol
pair by calling function
.Xr dwarf_get_relocation_info 3 .
The relocation entry for the first symbol will have type
.Dv dwarf_drt_first_of_length_pair
and the relocation entry for the second symbol will have type
.Dv dwarf_drt_second_of_length_pair .
.El
.Pp
If argument
.Ar err
is not NULL, it will be used to store error information in case
of an error.
.Pp
Function
.Fn dwarf_add_frame_fde
is similar to function
.Fn dwarf_add_frame_fde_b
except that it supports only one relocation symbol.
.Sh RETURN VALUES
On success, these functions return the index value for
the added frame descriptor.
In case of an error, these functions return
.Dv DW_DLV_NOCOUNT
and set the argument
.Ar err .
.Sh ERRORS
These functions can fail with:
.Bl -tag -width ".Bq Er DW_DLE_ARGUMENT"
.It Bq Er DW_DLE_ARGUMENT
One of the arguments
.Ar dbg
or
.Ar fde
was NULL.
.It Bq Er DW_DLE_ARGUMENT
The frame descriptor referenced by argument
.Ar fde
did not belong to the producer instance referenced by argument
.Ar dbg .
.It Bq Er DW_DLE_ARGUMENT
The common information entry index specified by argument
.Ar cie
was invalid.
.It Bq Er DW_DLE_ARGUMENT
Argument
.Ar end_symbol_index
was non-zero, but the flag
.Dv DW_DLC_SYMBOLIC_RELOCATIONS
was not set on the producer instance.
.El
.Sh SEE ALSO
.Xr dwarf 3 ,
.Xr dwarf_add_fde_inst 3 ,
.Xr dwarf_add_frame_cie 3 ,
.Xr dwarf_fde_cfa_offset 3 ,
.Xr dwarf_get_relocation_info 3 ,
.Xr dwarf_new_fde 3 ,
.Xr dwarf_producer_init 3 ,
.Xr dwarf_producer_init_b 3
